1. Field of the Invention
The present invention relates to a communication apparatus such as a node apparatus used for signal transmission and a network system using the apparatus, and a signal control method used in the network system, and more particularly, to a communication apparatus such as a node apparatus which constructs a network in a flexible manner and selects a transmission direction in a flexible manner, and corrects faults occurred in the network.
2. Description of Related Art
In recent years, a signal transmission construction using a plurality of channels has been studied to realize a high-speed and large capacity network connecting terminal devices. For example, Japanese Patent Application Laid-Open Nos. 8-172394, 8-237306 and 9-55758 disclose a transmission construction using a plurality of channels.
Prior to the explanation of the present invention, an example using a part of the construction disclosed in Japanese Patent Application Laid-Open No. 8-237306 will be described below.
FIG. 5 is a block diagram showing the construction of a node apparatus in a network of the example. The node apparatus is connected to terminals 551 to 558 via sub transmission paths. Reference numerals 501 to 508 denote separation inserting units as separation inserting means having a function for detecting an address of a packet inputted from parallel multiplex transmission paths and separating the packet into a packet to be transmitted to a terminal via a subtransmission path and a packet to be inputted into a buffer, and a function for inserting the packet transmitted from a terminal into a packet stream inputted from the parallel multiplex transmission paths. Numerals 511 to 518 denote buffers as buffer means having a function for temporarily storing a packet outputted from the separation inserting unit into a storage area corresponding to an output terminal of a switch 541. Numerals 521 to 528 and numerals 531 to 538 denote the parallel multiplex transmission paths of a plurality of channels for connecting nodes. The transmission paths are, e.g., a plurality of spatially separated optical fiber transmission paths or a wavelength multiplex transmission path wavelength-divided and multiplexed on one optical fiber. Numeral 541 denotes the switch, controlled by a switch controller 542, to connect a packet inputted into one of input terminals IN1 to IN8 to arbitrary one of output terminals OUT1 to OUT8. The switch 541 performs switching by using spatial switches when the parallel multiplex transmission paths are a plurality of optical fiber transmission paths. Further, when a wavelength multiplex transmission path is used, the switch is constructed between the nodes by connecting a transmission unit, comprising a plurality of variable-wavelength laser diodes and a wave combiner, to the wavelength multiplex transmission path such that a receiving unit of the wavelength multiplex transmission paths separates the respective wavelengths by using a wave separator, and the switching is performed by arbitrarily setting transmission wavelengths of the variable-wavelength laser diodes within a range of .lambda.1 to .lambda.8. The switching in this case is performed by an arrangement a little different from the arrangement as shown in FIG. 5. Numeral 542 denotes the switch controller which controls the switch in accordance with, for example, a control pattern in FIG. 4. Numeral 543 denotes a buffer controller. When the input terminals of the switches connected to the respective buffers are connected to desired output terminals, the buffer controller 543 read stored packets from the buffers.
FIG. 4 shows the control pattern indicative of the input-output connection relation of the switch 54 changed by control addresses A1 to A8. The input terminals IN1 to IN8 correspond to the buffers 511 to 518, and the output terminals OUT1 to OUT8 (or transmission wavelengths .lambda.1 to .lambda.8), to storage areas 1 to 8 of the respective buffers.
FIG. 6 shows an example of the construction of a network using the node apparatus in FIG. 5. In the system, four node apparatuses 601 to 604 are connected in a ring type construction with parallel multiplex transmission paths 605 to 608. The respective node apparatuses are connected to eight terminals 611 to 618 via eight subtransmission paths. The terminals 611 to 618 correspond to the terminals 551 to 558, and similarly, terminals 621 to 628, terminals 631 to 638, and terminals 641 to 648, to the terminals 551 to 558.
FIG. 7 is a block diagram for explaining the communication principle of this network. Numeral 701 to 704 denote node apparatuses; 705 to 708, switches corresponding to the switch 541; 709 to 712, buffers corresponding to the buffers 511 to 518; 721 to 736, terminals; and A to D, ring-shaped parallel transmission paths.
First, the communication principle of the network will be described with reference to FIG. 7. This network has the plurality of rings A to D, interconnected by the switches 705 to 709. The respective terminals are connected to one of ring transmission paths A to D. Upon communication with another terminal connected to another ring transmission path, the ring of the terminal is switched to the other ring by an arbitrary switch at least once. The position of switching is not specified, however, if the transmission path is switched to the destination transmission path at a node prior to the destination node, and at another node, the transmission path is switched to an arbitrary path, the communication control is easily made. In the network, in order to simplify the node apparatus, the switches 705 to 708 change the input-output connection relation in accordance with a specific circular pattern at predetermined periods regardless of input signals. The input signals are temporarily stored at the buffers 709 to 712. When the input-output connection relation of the switches becomes a desired relation, the packets are read from the buffer.
For example, if the terminal 722 performs communication with the terminal 732, a packet outputted from the terminal 722 is stored into the buffer 709 of the node 701, and when the input terminal IN3 is connected to the output terminal OUT2 in the switch 705, the packet is read from the buffer to the transmission path B. The packet is inputted into the buffer 710 of the node 702, and when the input terminal IN2 and the output terminal OUT4 of the switch 706 are connected, the packet is read from the buffer 710 to the transmission path D. Then, the packet is sent to the terminal 732.
In this manner, communication is performed by switching to an arbitrary ring in the respective node apparatuses.
Next, the details will be described with reference to FIGS. 5 and 6. In the explanation, the parallel multiplex transmission paths are a plurality of spatially separated optical fiber transmission paths. The switch is a spatial switch. In use of wavelength multiplex transmission path, as the communication is based on the above principle, substantially the same operation is performed. Next, an operation example where communication is performed between the terminals 612 and 635 will be described Transmission data from the terminal 612 is divided into fixed-length packets. Then, a destination address is written in the header of each packet, and the packet is outputted. The output packet is inputted through the sub transmission path into the node apparatus 601, and inserted into a gap in a packet stream from the parallel multiplex transmission path 521 by the separation inserting unit 502, and sent to the buffer 512. In the buffer 512, as the destination address of the input packet does not coincide with a pre-stored address of an adjacent downstream node apparatus, the packet is stored into an arbitrary storage area. In this example, the packet is stored in the storage area 1. The buffer controller 543 controls reading of the packet to be suspended until the input terminal IN2 is connected to the output terminal OUT1 in the switch 541, and when the terminals are connected, reads the packet. The switch controller 542 sequentially supplies control addresses A1 to A8 as shown in a table of FIG. 4, to change the connection relation of the switch 541, thus controls the control pattern to be repeated at 8-packet periods by supplying the control addresses at, e.g., one-packet periods. The information on the control address pattern is notified to the buffer controller 543 to control the timing of reading from the buffer. In this example, when the input terminal IN2 is connected to the output terminal OUT1 in the switch 541, the packet is read from the storage area 1 of the buffer 512, and the packet is outputted through the switch 541 to the transmission path 531. The packet transmitted via the transmission path 531 is inputted into the node apparatus 602, and inputted through the separation inserting unit 501 into the buffer 511. In the buffer 511, as the destination address detected from the header coincides with the address of an adjacent downstream node apparatus, a storage area is designated in correspondence with a transmission path connected to the terminal of the destination address. In this example, as the destination terminal is connected to the transmission path 535, the packet is stored into the storage area 5. When the input terminal IN1 is connected to the output terminal OUT 5 in the switch 541, the buffer controller 543 reads the packet from the storage area 5 of the buffer 511 to the transmission path 535 through the switch 541. Then, the packet is inputted through the transmission path into the separation inserting unit 505 of the node apparatus 603. As the destination address is that of the terminal connected to the separation inserting unit 505, the packet is separated from the transmission path and outputted into a direction for the terminal. The packet outputted from the separation inserting unit 505 is sent through the submission transmission path to the terminal 635, and received there.
Further, Japanese Patent Application Laid-open No. 9-261259 discloses connecting node apparatuses to bi-directional (in first and second directions) transmission paths, and outputting a packet received from a transmission path in the first direction to a transmission path in the second direction.
However, in the above node apparatus, when the transmission path for the packet is changed from a channel in the first direction to a channel in the second direction, the packet from the channel in the first direction is transmitted only to a specific channel in the second direction.
That is, the direction of the transmission paths is changed by transmitting the packet to a channel in the second direction corresponding to a channel in the first direction, e.g., from a first channel in the first direction to a first channel in the second direction, from a second channel in the first direction to a second channel in the second direction, from a third channel in the first direction to a third channel in the second channel.
Further, Japanese Patent Application Laid-Open No. 9-121229 discloses connecting node apparatuses to bi-directional (in first and second directions) transmission paths and outputting only a packet received from a specific channel in the first direction to a specific channel in the second direction.